1. Field of the Invention
This invention relates to a forging machine, more particularly to a feeding mechanism for a forging machine, which feeds an elongated blank to be forged.
2. Description of the Related Art
In the art of manufacturing nuts or bolts, a feeding mechanism is provided on a forging machine for feeding an elongated blank to be forged prior to thread formation. Referring to FIG. 1, a conventional feeding mechanism 1 is shown to include a machine frame 110, and two roller units, each of which consists of a pair of upper and lower feeding rollers 11 for clamping and moving an elongated blank 10 therebetween. Referring to FIGS. 2, 3 and 4, each of the rollers 11 is provided coaxially with a fixed rotating shaft 111, which is journalled on the machine frame 110 by means of bearings 112 and which is connected coaxially and fixedly to a driven gear 13. Upper driven gears 13 mesh with lower driven gears 13, respectively. A driving member 14 includes a driving gear 141 and a ratchet wheel 142, which are connected coaxially and fixedly with each other. The driving gear 141 is provided coaxially with a fixed rotating shaft 140, which is journalled on the machine frame 110. A swing arm 15 is sleeved rotatably on the rotating shaft 140 at an upper end thereof, and is connected pivotally to a left end of a push-pull rod 16 at a lower end thereof. A right end of the push-pull rod 16 is connected rotatably to a crank pin 180 of a crank member 18, which has a crank shaft 181. When the swing arm 15 is swung by the push-pull rod 16 to rotate the driving member 14, a linkage 151 presses intermittently a pawl member 152 against a toothed outer periphery of the ratchet wheel 142 so as to rotate the ratchet wheel 142 counterclockwise and intermittently, thereby permitting intermittent unidirectional rotation of the driving gear 141 on the machine frame 110 and each of the rollers 11. The blank 10 is fed a predetermined distance at each time, in which the swing arm 15 effects a swinging cycle. The predetermined distance depends on the distance between the crank shaft 181 and the crank pin 180. A braking member 143 is mounted on the machine frame 110, and has a circumferentially extending brake plate 144, which presses against an outer periphery of the rotating shaft 140 for preventing untimely rotation of the rotating shaft 140 on the machine frame 110. A relatively large force to drive the push-pull rod 16 is required to overcome the gripping force of the braking member 143 on the rotating shaft 140 and to rotate the rollers 11, the driven gears 13, the driving gear 141, the ratchet wheel 142, the swing arm 15, and the linkage 151. As a result, it is difficult to start and stop the rotation of the driving member 14. As such, the brake plate 144 wears easily so that the pawl member 152 engages a tooth of the ratchet wheel 142 at a point 148, thereby subsequently sliding to a point 149, in which the pawl member 152 can push a tooth of the ratchet wheel 142 to rotate counterclockwise, as shown in FIG. 5. This sliding movement of the pawl member 152 generates noise, and affects adversely the quality of the forged products in view of the condition that the distance of the blank 10, which is fed by the feeding mechanism 1 is uneven.